Semiconductor device manufacturing method and chemical mechanical polishing method

ABSTRACT

According to one embodiment, a semiconductor device manufacturing method comprises forming a film to be polished on a semiconductor substrate, and performing a CMP method on the film to be polished. The CMP method includes polishing the film to be polished by bringing a surface of the film to be polished into contact with a surface of a polishing pad having a negative Rsk value.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2012-132383, filed Jun. 11, 2012, theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a semiconductor devicemanufacturing method and chemical mechanical polishing method.

BACKGROUND

Semiconductor device manufacturing steps include shallow trenchisolation (STI)-chemical mechanical polishing (CMP) and pre-metaldielectric (PMD)-CMP. In these CMP methods, a film to be polished suchas a silicon oxide film formed on a semiconductor substrate isplanarized.

For example, a ceria-based slurry is used in the planarization (CMP) ofa silicon oxide film. The ceria-based slurry has a high polishing ratefor a silicon oxide film, and has a high planarization performance. Evenwhen using the ceria-based slurry, however, many scratches are producedon the surface of a film to be polished (silicon oxide film) after CMP,depending on the surface state of a polishing pad. As a consequence, theyield and reliability decrease.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing the arrangement of a CMP apparatus according toan embodiment;

FIG. 2 is a plan view showing the CMP apparatus according to theembodiment;

FIG. 3 is a flowchart showing a semiconductor device manufacturingmethod according to the embodiment;

FIG. 4 is a view for explaining the Rsk value;

FIG. 5 is a graph showing the relationship between the Rsk value on thesurface of a polishing pad and the number of scratches on the surface ofa film to be polished in a polishing experiment;

FIG. 6 is a graph showing the relationship between the surfacetemperature and Rsk value of a polishing pad in a conditioningexperiment; and

FIGS. 7 and 8 are sectional views showing semiconductor device STImanufacturing steps according to the embodiment.

DETAILED DESCRIPTION

In general, according to one embodiment, a semiconductor devicemanufacturing method comprises forming a film to be polished on asemiconductor substrate, and performing a CMP method on the film to bepolished. The CMP method includes polishing the film to be polished bybringing a surface of the film to be polished into contact with asurface of a polishing pad having a negative Rsk value.

This embodiment will be explained below with reference to theaccompanying drawings. In these drawings, the same reference numbersdenote the same parts. Also, a repetitive explanation will be made asneeded.

Embodiment

The embodiment will be explained with reference to FIGS. 1, 2, 3, 4, 5,6, 7, and 8. In this embodiment, in a CMP method of a semiconductordevice manufacturing method, the surface of a polishing pad 11 isconditioned such that the Rsk value becomes negative, and a film to bepolished is brought into contact with (slid against) the rotatingpolishing pad 11. This can reduce scratches on the surface of the filmto be polished after CMP. The semiconductor device manufacturing methodaccording to the embodiment will be explained in detail below.

[CMP Apparatus]

First, a CMP apparatus according to this embodiment will be explainedbelow with reference to FIGS. 1 and 2.

FIG. 1 is a view showing the arrangement of the CMP apparatus accordingto the embodiment. FIG. 2 is a plan view showing the CMP apparatusaccording to the embodiment.

As shown in FIG. 1, the CMP apparatus according to this embodimentincludes a turntable 10, polishing pad 11, top ring 12, slurry supplynozzle 13, dressing liquid supply nozzle 14, dresser 15, and inlettemperature measurement device 16.

The top ring 12 holding a semiconductor substrate 20 is brought intocontact with the polishing pad 11 attached to the turntable 10. A filmto be processed such as a silicon oxide film is formed on thesemiconductor substrate 20. The turntable 10 can rotate at 1 to 200 rpm,and the top ring 12 can also rotate at 1 to 200 rpm. The turntable 10and top ring 12 rotate in the same direction, for example,counterclockwise. Also, the turntable 10 and top ring 12 rotate in apredetermined direction during CMP. The polishing load of these membersis normally about 50 to 500 hPa.

The slurry supply nozzle 13 is positioned above the polishing pad 11.The slurry supply nozzle 13 can supply a predetermined liquid chemicalas a slurry at a flow rate of 50 to 1,000 cc/min. Note that the slurrysupply nozzle 13 is positioned near the center of the turntable 10, butthe position is not limited to this, and the slurry supply nozzle 13 mayalso appropriately be positioned so as to supply the slurry on theentire surface of the polishing pad 11.

The dresser 15 conditions the surface of the polishing pad 11 whenbrought into contact with the polishing pad 11. The dresser 15 canrotate at 1 to 200 rpm. The dresser 15 rotates, for example,counterclockwise. Also, the turntable 10 and dresser 15 rotate in apredetermined direction during conditioning. The dressing load of thedresser 15 is normally about 50 to 500 hPa. The inlet temperaturemeasurement device 16 as an infrared radiation thermometer is attachedto a pillar portion (dresser driving shaft) connected to the dresser 15.Details of the inlet temperature measurement device 16 will be describedlater.

In addition, the dressing liquid supply nozzle 14 is positioned abovethe polishing pad 11. The dressing liquid supply nozzle 14 can supply apredetermined liquid as a dressing liquid at a flow rate of 50 to 1,000cc/min. Note that the dressing liquid supply nozzle 14 is positionednear the center of the turntable 10, but the position is not limited tothis, and the dressing liquid supply nozzle 14 may also appropriately bepositioned so as to supply the dressing liquid on the entire surface ofthe polishing pad 11.

The dressing liquid is, for example, pure water, and the supplytemperature of the liquid is appropriately set. By controlling thisdressing liquid supply temperature, the inlet temperature to be measuredby the inlet temperature measurement device 16 can be adjusted.

As shown in FIG. 2, the inlet temperature measurement device 16 isinstalled upstream in the rotating direction of the turntable 10 withrespect to the dresser 15. Therefore, the inlet temperature measurementdevice 16 measures the surface temperature (inlet temperature) of thepolishing pad 11 on the upstream side in the rotating direction of theturntable 10 with respect to the dresser 15.

The inlet temperature measurement device 16 measures the temperature ofthe polishing pad 11 on a circular orbit X passing a center O′ of thedresser 15 and having a predetermined distance from a center O of theturntable 10. This is so because the time during which the dresser 15and polishing pad 11 are in contact with each other is long on thecircular orbit X, and so the highest temperature can be measured.

Near the edge of the dresser 15, the dressing liquid collides againstthe dresser 15 and rises. When temperature measurement is performed nearthe edge of the dresser 15, therefore, the inlet temperature measurementdevice 16 may measure not the surface temperature of the polishing pad11 but the temperature of the dressing liquid by mistake. To measure thesurface temperature of the polishing pad 11, the inlet temperaturemeasurement device 16 desirably measures the temperature at an inlettemperature measurement point A positioned on the circular orbit X andspaced apart by a distance d (for example, 10 mm) from the dresser 15.

Note that when the dressing liquid is supplied to the entire surface ofthe polishing pad 11, it is possible to measure the temperature at anypoint on the surface of the polishing pad 11, including the inlettemperature measurement point A, as the surface temperature of thepolishing pad 11. That is, the inlet temperature measurement device 16can be installed in any position as long as the temperature at any pointon the surface of the polishing pad 11 can be measured.

[Manufacturing Method]

Next, the semiconductor device manufacturing method according to thisembodiment will be explained with reference to FIG. 3.

FIG. 3 is a flowchart showing the semiconductor device manufacturingmethod according to the embodiment.

As shown in FIG. 3, in step S1, a film to be polished is formed on thesemiconductor substrate 20. This film to be polished is, for example, asilicon oxide film when forming an STI structure or PMD structure, butis not limited to this.

Then, in step S2, a CMP method is performed on the film to be polished.In this step, the CMP method according to this embodiment is performedunder the following conditions.

First, in step S21, the polishing pad 11 is conditioned. Morespecifically, the dresser 15 is brought into contact with the surface ofthe polishing pad 11, and slid against the polishing pad 11. Inaddition, the dressing liquid supply nozzle 14 supplies the dressingliquid, for example, pure water to the surface of the polishing pad 11.

As the polishing pad 11, a material mainly containing polyurethane andhaving a Shore D hardness of 50 (inclusive) to 80 (inclusive) and amodulus of elasticity of 200 (inclusive) to 700 (inclusive) MPa isattached to the turntable 10. Also, the rate of rotation of theturntable 10 is set at, for example, 10 (inclusive) to 110 (inclusive)rpm. As the dresser 15, a material having a diamond roughness of #100(inclusive) to #200 (inclusive) (manufactured by Asahi Diamond) is used.The rate of rotation of the dresser 15 is set at 10 (inclusive) to 110(inclusive) rpm, and the dressing load is set at 50 (inclusive) to 300(inclusive) hPa. The conditioning time is set at 60 s.

When supplying pure water, the supply temperature and supply flow rateof the pure water are controlled so that the surface temperature of thepolishing pad 11 (the temperature measured at the inlet temperaturemeasurement point A by the inlet temperature measurement device 16) is23° C. or more. Consequently, the Rsk value of the polishing pad 11 canbe set at −0.5 or less.

Then, the film to be polished is polished in step S22. Morespecifically, the film to be polished held by the top ring 12 is broughtinto contact with the conditioned polishing pad 11, and slid against thepolishing pad 11. The rate of rotation of the top ring 12 is set at, forexample, 120 rpm, and the polishing load is set at, for example, 300gf/cm². Also, the slurry supply nozzle 12 supplies the slurry at a flowrate of 100 cc/min. The slurry contains cerium oxide (DLS2 manufacturedby Hitachi Chemical) as abrasive grains and ammonium polycarboxylate(TK75 manufactured by Kao).

By thus polishing the film to be polished by bringing its surface intocontact with the surface of the rotating polishing pad 11 having an Rskvalue of −0.5 or less, the number of scratches on the surface of thepolished film can be reduced. The basis for this will be describedlater.

Note that the Rsk value on the surface of the polishing pad 11 isdesirably −0.5 or less, and more desirably, −1.0 or less. However, theRsk value on the surface of the polishing pad 11 is not limited to this,and need only be negative. As will be described later, when the surfacetemperature of the polishing pad 11 is raised during conditioning, theRsk value of the polishing pad 11 decreases (i.e., the Rsk value becomesa negative value having a large absolute value). That is, the Rsk valueis desirably decreased by raising the surface temperature of thepolishing pad 11 during conditioning. However, the Rsk value of thepolishing pad 11 may only be a negative value even when the surfacetemperature of the polishing pad 11 is less than 23° C.

FIG. 4 is a view for explaining the Rsk value.

The Rsk value (roughness curve skewness value) indicates the relativityof a probability density distribution with respect to the average lineof a surface roughness profile.

When the probability density distribution is biased below the averageline of the surface roughness profile as indicated by (a) in FIG. 4, theRsk value is positive. In this state, the number of projecting portionsis large, and that of flat portions is small.

On the other hand, when the probability density distribution is biasedabove the average line of the surface roughness profile as indicated by(b) in FIG. 4, the Rsk value is negative. In this state, the number ofprojecting portions is small, and that of flat portions is large.

That is, the surface is smoother when the Rsk value is negative thanwhen it is positive.

[Basis of CMP Conditions]

The basis of the CMP conditions according to this embodiment will now beexplained with reference to FIGS. 5 and 6.

First, a polishing experiment for checking the relationship between theRsk value on the surface of the polishing pad 11 and the number ofscratches on the surface of a film to be polished was conducted.

FIG. 5 is a graph showing the relationship between the Rsk value on thesurface of the polishing pad 11 and the number of scratches on thesurface of the film to be polished in the polishing experiment. The Rskvalue herein mentioned was calculated from the roughness measured by ahigh-field laser microscope, for example, HD100D (manufactured byLasertec). The number of scratches was counted by a KLA2815(manufactured by KLA-Tencor, SEM Review) after the surface of the filmto be polished was lightly etched with diluted hydrofluoric acid afterCMP.

As shown in FIG. 5, when the surface of a film to be polished ispolished by bringing the surface into contact with the surface of thepolishing pad 11, there is a positive correlation (correlationcoefficient=0.71) between the Rsk value on the surface of the polishingpad 11 and the number of scratches produced by the polishing on thesurface of the film to be polished. In other words, the number ofscratches on the surface of the film to be polished increases when theRsk value of the polishing pad 11 increases, and decreases when the Rskvalue decreases.

Also, as the Rsk value on the surface of the polishing pad 11 increasestoward the negative side (as the absolute value of the negative Rskvalue increases), the number of scratches on the surface of the film tobe polished decreases, and the variation in number decreases. Especiallywhen the Rsk value on the surface of the polishing pad 11 is −0.5 orless, more desirably, −1.0 or less, the number of scratches on thesurface of the film to be polished further decreases, and the variationin number further decreases.

As described above, the number of scratches on the surface of the filmto be polished can be decreased by polishing the film by setting the Rskvalue on the surface of the polishing pad 11 at a negative value havinga large absolute value. Accordingly, the Rsk value on the surface of thepolishing pad 11 is desirably set at a negative value having a largeabsolute value by conditioning.

Then, a conditioning experiment for checking the relationship betweenthe surface temperature and Rsk value of the polishing pad 11 wasconducted. In this experiment, the surface temperature of the polishingpad 11 to be measured by the inlet temperature measurement device 16 wasadjusted by controlling the dressing liquid to be supplied from thedressing liquid supply nozzle 14 in the above-described CMP apparatus.The conditioning experiment was conducted under the followingconditions.

Polishing pad: Polyurethane (Shore D hardness=60, modulus ofelasticity=400 MPa)Turntable rate of rotation: 20 rpmDresser: Diamond roughness=#100 (available from Asahi Diamond)Dresser load: 200 hPaDresser rate of rotation: 20 rpm

Conditioning experiments were conducted for 60 sec by using pure wateras the dressing liquid, and setting the supply temperature at 5, 23(room temperature), and 65° C. In these conditioning experiments, thesurface temperatures of the polishing pad 11 measured by the inlettemperature measurement device 16 were 9, 23, and 41° C.

FIG. 6 is a graph showing the relationship between the surfacetemperature and Rsk value of the polishing pad 11 in the conditioningexperiment.

As shown in FIG. 6, when conditioning the surface of the polishing pad11 by the dresser 15, there is a negative correlation between thesurface temperature of the polishing pad 11 during the conditioning, andthe resultant Rsk value of the polishing pad 11. In other words, the Rskvalue of the polishing pad 11 decreases when the surface temperature ofthe polishing pad 11 rises, and increases when the surface temperaturedecreases. More specifically, the Rsk values of the polishing pad 11 are−0.43, −0.56, and −0.78 when the surface temperatures of the polishingpad 11 are 9, 23, and 41° C., respectively.

As described above, the Rsk value on the surface of the polishing pad 11is desirably set at a negative value having a large absolute value byconditioning. The Rsk value on the surface of the polishing pad 11 canbe set at a negative value having a large absolute value by increasingthe surface temperature of the polishing pad 11 during conditioning. Forexample, when supplying pure water in conditioning, the Rsk value on thesurface of the polishing pad 11 can sufficiently be set at −0.5 or lessby setting the surface temperature of the polishing pad 11 at 23° C. ormore.

On the other hand, the polishing rate of the polishing pad 11 duringconditioning depends on the surface temperature of the polishing pad 11.The polishing rate decreases when the surface temperature of thepolishing pad 11 rises, and increases when the surface temperaturedecreases. More specifically, the polishing rates of the polishing pad11 during conditioning are 0.9, 0.5, and 0.05 μm/min when the surfacetemperatures of the polishing pad 11 are 9, 23, and 41° C.,respectively. This is so probably because when the surface temperatureof the polishing pad 11 rises, the polishing pad 11 softens (the modulusof elasticity decreases), and polishing becomes difficult. That is, theuseful life of the polishing pad 11 can be prolonged by raising thesurface temperature of the polishing pad 11.

As described above, when performing conditioning by raising the surfacetemperature of the polishing pad 11, it is possible to set the Rsk valueof the polishing pad 11 at a negative value having a large absolutevalue, and decrease the polishing rate of the polishing pad 11.

Note that the surface temperature of the polishing pad 11 is the inlettemperature of the polishing pad 11 measured by the inlet temperaturemeasurement device 16, and can be measured at any point on the surfaceof the polishing pad 11 when the dressing liquid is supplied on theentire surface of the polishing pad 11.

[Effects]

In the CMP method of the semiconductor device manufacturing methodaccording to the abovementioned embodiment, after the surface of thepolishing pad 11 is conditioned at a high temperature, a film to bepolished is polished by bringing its surface into contact with thesurface of the polishing pad 11. This can achieve the following effects.

Since the surface of the polishing pad 11 is conditioned at a highertemperature, the Rsk value on the surface of the polishing pad 11 can beset at a negative value having a larger absolute value. For example,when supplying pure water in conditioning, the Rsk value on the surfaceof the polishing pad 11 can be set at −0.5 or less by setting thesurface temperature of the polishing pad 11 at 23° C. or more. When afilm to be polished is polished by bringing its surface into contactwith the surface of the polishing pad 11 having this negative Rsk value,the number of scratches on the surface of the film to be polished afterCMP can be reduced. Consequently, it is possible to suppress thedecrease in device yield and reliability.

It is also possible to decrease the polishing rate of the polishing pad11 by conditioning the surface of the polishing pad 11 at a highertemperature. This makes it possible to prolong the service life of thepolishing pad 11, and reduce the cost of the CMP step.

Application Example

An application example of the semiconductor device manufacturing methodaccording to this embodiment will be explained below with reference toFIGS. 7 and 8. In this example, a method of manufacturing an STIstructure in a semiconductor device will be explained.

FIGS. 7 and 8 are sectional views showing semiconductor device STImanufacturing steps according to the embodiment.

First, as shown in FIG. 7, a silicon nitride film 21 functioning as astopper film is formed on a semiconductor substrate 20. After that, STIpatterns 22 are formed in the semiconductor substrate 20 by using asilicon oxide film or the like as an etching mask. Note that it is alsopossible to form, for example, a silicon oxide film between thesemiconductor substrate 20 and silicon nitride film 21.

Then, a silicon oxide film 23 is formed on the entire surface by, forexample, high-density plasma chemical vapor deposition (CVD). In thisstep, the silicon oxide film 23 is formed outside the STI patterns 22.

Subsequently, as shown in FIG. 8, CMP is performed using the siliconoxide film 23 as a film to be processed, thereby polishing the surfaceof the film. The embodiment is applied to this CMP step. That is, afterconditioning is performed such that the Rsk value on the surface of thepolishing pad 11 becomes a negative value, the silicon oxide film 23 ispolished by bringing its surface into contact with the surface of thepolishing pad 11. Consequently, the silicon oxide film 23 outside theSTI patterns 22 is removed, and an STI structure is formed.

The present embodiment is not limited to this, and the CMP methodaccording to this embodiment is applicable to CMP performed for variousmetal materials and various insulating materials as films to beprocessed.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A semiconductor device manufacturing methodcomprising: forming a film to be polished on a semiconductor substrate;and performing a CMP method on the film to be polished, wherein the CMPmethod includes polishing the film to be polished by bringing a surfaceof the film to be polished into contact with a surface of a polishingpad having a negative Rsk value.
 2. The method of claim 1, wherein theRsk value is not more than −0.5.
 3. The method of claim 1, wherein theRsk value is not more than −1.0.
 4. The method of claim 1, whereinbefore the polishing the film to be polished, the CMP method furthercomprises conditioning the polishing pad by bringing a dresser intocontact with the surface of the polishing pad while supplying pure waterto the surface of the polishing pad.
 5. The method of claim 4, wherein asurface temperature of the polishing pad is not less than 23° C. in theconditioning the polishing pad.
 6. The method of claim 5, wherein thepolishing pad is rotated in the conditioning the polishing pad, and thesurface temperature of the polishing pad is an inlet temperature of thepolishing pad on an upstream side in a rotating direction with respectto the dresser.
 7. The method of claim 5, wherein the surfacetemperature of the polishing pad is controlled by a supply temperatureand supply flow rate of the pure water.
 8. The method of claim 4,wherein the polishing pad is rotated in the conditioning the polishingpad, and a rate of rotation of the polishing pad is 10 (inclusive) to110 (inclusive) rpm.
 9. The method of claim 4, wherein the dresser isrotated in the conditioning the polishing pad, and a rate of rotation ofthe dresser is 10 (inclusive) to 110 (inclusive) rpm.
 10. The method ofclaim 4, wherein a load of the dresser to be brought into contact withthe surface of the polishing pad is 50 (inclusive) to 300 (inclusive)hPa.
 11. The method of claim 1, wherein the polishing pad containspolyurethane as a main material, and has a Shore D hardness of 50(inclusive) to 80 (inclusive) and a modulus of elasticity of 200(inclusive) to 700 (inclusive) MPa.
 12. The method of claim 1, whereinthe film to be polished is a silicon oxide film to be used as an STIstructure.
 13. A chemical mechanical polishing method comprisespolishing a film to be polished formed on a substrate by bringing asurface of the film to be polished into contact with a surface of apolishing pad having a negative Rsk value.
 14. The method of claim 13,wherein the Rsk value is not more than −0.5.
 15. The method of claim 13,wherein the Rsk value is not more than −1.0.
 16. The method of claim 13,further comprising, before the polishing the film to be polished,conditioning the polishing pad by bringing a dresser into contact withthe surface of the polishing pad while supplying pure water to thesurface of the polishing pad.
 17. The method of claim 16, wherein asurface temperature of the polishing pad is not less than 23° C. in theconditioning the polishing pad.
 18. The method of claim 17, wherein thepolishing pad is rotated in the conditioning the polishing pad, and thesurface temperature of the polishing pad is an inlet temperature of thepolishing pad on an upstream side in a rotating direction with respectto the dresser.
 19. The method of claim 17, wherein the surfacetemperature of the polishing pad is controlled by a supply temperatureand supply flow rate of the pure water.
 20. The method of claim 13,wherein the polishing pad contains polyurethane as a main material, andhas a Shore D hardness of 50 (inclusive) to 80 (inclusive) and a modulusof elasticity of 200 (inclusive) to 700 (inclusive) MPa.